This invention relates to an anode for the internal protection of hollow corrodible metallic substrates wherein the anode incorporates a magnetic holddown means.
Metallic anodes for the internal protection of hollow corrodible substrates are known. When the anode is not to be sacrificial, it may be plated with a thin layer of a precious metal such as platinum. Such an anode is often placed inside a porous jacket to protect the thin plating layer of precious metal from damage, since any damage could result in exposure of the anode base material followed by corrosion, thereby leading to failure of the anode.
In copending and commonly assigned U.S. application Ser. No. 272,854, filed June 12, 1981 now abandoned and entitled "Corrosion Protection System", the disclosure of which is incorporated herein by reference, there is disclosed a flexible conductive polymeric anode suitable for the internal protection of hollow corrodible metallic substrates by means of impressed current protection. Such an anode has the advantages over conventional anodes of flexibility and electrochemical stability.
However, an internal anode is subject to abrasion against the internal surface of the substrate, such as a pipe in which it is placed, should there be flow, especially turbulent flow, of the fluid passing through. Also, though most pipes, tanks, etc. which are used for the conveyance and storage of corrosive fluids are internally coated with a non-conductive, corrosion-resistant layer (such as an epoxy), bare metal may be exposed and there therefore is the possibility of a short-circuit between the anode and substrate should they come into contact, leading to the loss of corrosion protection.
In the '854 application, it was proposed to adhere the conductive polymeric anode to the substrate with an adhesive, and/or to protect it with a porous jacket, such as a braid.
The use of an adhesive is sometimes unsatisfactory both because the anode may not adhere well to e.g. a dirty substrate, and because installation of an adhesive-coated anode will be difficult due to adhesion at undesired locations.
Protecting the anode by means of a porous jacket is a useful technique, but abrasion can still occur when the jacket is damaged.
It is therefore desirable to develop a method for preventing the anode of a corrosion protection system from (a) abrasion against the substrate, and (b) accidential electrical contact with the substrate during use. The anode should also be capable of facile installation.